There are many yellow spots on the leaves of corn. What is the reason?

Corn leaf spot is rare in the early growth stage. Especially because the incidence will increase after germination. In fact, the real big spot can be well judged in the later stage. As shown in the above picture, there is such a yellow spot in the middle of the green leaves, but it was blue-gray in the early stage. The occurrence of maize leaf spot is closely related to four aspects. One is variety, the other is climate, the third is planting, and the fourth is soil, which is simply a variety of fragile diseases. The incidence rate is very high, and the plots with poor soil are more serious than the fertile plots. Over-dense planting density is more serious than normal standing trees, and plots with poor gout are more serious than plots with good ventilation, and there is a proportion of continuous cropping.

If you don't know how to choose, you can go to the agricultural store to ask, or look at the incidence of corn and leaf blight planted last year. If the incidence is less, you can continue to use it. On the contrary, if there are many diseases, it is necessary to change varieties. Not only corn, but also other crops. You can't continue to grow some crops for many years. Please don't apply trace elements such as nitrogen fertilizer, phosphorus fertilizer and potassium alone in fertilizer application. If the preventive measures are not appropriate, filariasis has occurred, and the commonly used drugs are triazolam, carbendazim, benzoxazole, pyrazinamide and so on. These medicines are not expensive either. Pay attention to infiltration when using drugs, and you can't prevent the land with serious illness at one time, and the interval is also 7.

The pathogen of maize brown spot disease is Yu Shujie, and the pathogen is resting spore, which overwinters on the ground or on the diseased body. In the second year, the pathogen spread to maize plants through airflow, and when it germinated under suitable conditions, it produced a large number of zoospores, which swam in the water droplets on the surface of leaves to form infiltration chambers and invaded the soft tissue of maize. The strain likes high temperature and high humidity, and the germination of dormant sporangium needs water drop condition and temperature of 23 ~ 30℃. High temperature, high humidity and rainy in July and August are conducive to the onset. In the plot with poor soil, the leaves turn yellow and the disease is serious. In the plot with high soil fertility, the corn is solid, with thick leaves and green leaves, and the disease is light and does not occur. Generally speaking, corn with 8 ~ 10 leaves is easy to get sick, and corn with 12 leaves will not get sick again.

The disease mainly occurs on leaves, leaf sheaths and stems of maize, and there are many spots at the intersection of leaves and leaf sheaths. It first occurs at the top of 4 ~ 8 blade tips. The mole initially changed from round or oval to linear white or yellow spots, and the mesophyll faded to red. Many small spots are usually connected together to form a horizontal bandwidth macula. In the later period, cavalry tissues gradually turned brown or dark brown, healed into large and irregular spots, and blood vessels often burst one after another, resulting in the failure of leaves to provide nutrition and wither and die, which had a great impact on yield. The disease can reduce the yield of maize by 10% to 20%, and seriously reduce the yield by 40%.